Anatomical and morphological study of the kidneys of the breeding emu (Dromaius novaehollandiae)

Abstract

We analyzed 16 kidneys obtained from 15-year-old emus, Dromaius novaehollandiae. Emus were kept at an experimental farm in Poland. The results showed that each kidney was composed of 3 parts: cranial, medial, and caudal divisions. Histological results demonstrated that the kidneys consisted of 2 zones: the cortex and the medulla. The cortex made up the majority of the kidney, while the medulla formed only a small portion of the organ. Proximal and distal tubules and 2 types of glomeruli (looped and loopless) were localized in the cortex. Each of these glomeruli was characterized by tightly arranged mesangial cells. Proximal and distal tubules had a distinctive simple low cuboidal epithelium. The luminal surface of the proximal tubules had a brush border membrane, formed by numerous microvilli. The renal medulla of emu kidneys formed irregularly positioned characteristic cones of different sizes. The medulla was composed of thin and thick segments of Henle's loops lined with a simple cuboidal epithelium and collecting ducts with a simple columnar epithelium. In the absence of detailed information in the literature about the anatomy and morphology of emu kidneys, our study provides new information and undoubtedly complements the knowledge in this field with respect to this species of bird.